How Does 'The Flash' Know 'Supergirl'? The Heroes Have Already Shared An Adventure

The big CW superhero crossover between Supergirl, The Flash, Arrow, and Legends of Tomorrow is finally happening. While Kara Danvers may be new to the network, this isn't the first time that she's meeting these heroes, as The Flash and Supergirl already know each other. For those of you who aren't familiar with the Kryptonians, here's a quick recap of how they first met.

The two supers first met in the Season 1 episode of Supergirl titled "World's Finest," which debuted on CBS in March. Barry, who was training his speed in order to face Zoom, tore through dimensions and ended up in Supergirl's world. There, Barry gave Kara some tips on protecting a city and maintaining a secret identity while her friends figured out a way to speed him back to his own Earth.

Unsurprisingly, these two sunny personalities got along right away. That's the great thing about these particular heroes; most of the time, there isn't a drop of angst between them. Their chemistry wasn't exactly romantic. Both Kara and Barry were dealing with their own relationship woes at the time. However, they made a great team both as crime fighters and as friends. Also, Barry used his powers to get everyone ice cream. Why isn't he speed delivering food to everyone, all the time?

Weirdly, the crossover was never really acknowledged on The Flash — which, in my opinion, was at the time a missed opportunity to tell Cisco Ramon about the existence of aliens. Kara, James, and Winn got to learn all about the multiverse. However, the team at S.T.A.R. Labs didn't get to learn about Barry's adventures with Kara Zor-El on screen. In the episode "Versus Zoom." we see the speed test that sent Barry to Kara's world, but that's it.

At least this crossover won't be the last of their partnership. A musical Flash/Supergirl crossover is coming as well. It's always fun when Arrow characters get to have fun on The Flash, and Kara and Barry's friendship that Supergirl established was so charming, I can't wait to add more characters to the mix.